`programs.shfmt.indent_size = null` uses tabs rather than `.editorconfig` setting

I'm migrating to treefmt-nix from pre-commit, and noticed that `shfmt` by default ignores `.editorconfig`. But [setting `programs.shfmt.indent_size = null`](https://github.com/numtide/treefmt-nix/blob/5b4ee75aeefd1e2d5a1cc43cf6ba65eba75e83e4/programs/shfmt.nix#L32-L40) doesn't work either – all the indentation is changed to tabs. The relevant settings: ``` root = true [*] indent_size = 4 indent_style = space ```